With present day technology, the need for lightweight portable computers, such as laptop and notebook type computers, has increased extensively. Portable computers need to have low weight as well as being compact, so that the user can carry and transport the computer from one location to another without difficulty. A significant part of the weight of the computer is the battery that provides the power necessary for operating the portable computer when a commercial power outlet is not available. When a standard commercial power source or outlet, providing 110 volts or 120 volts, is available, there is sufficient power to achieve high performance operation, with or without utilizing the battery. If a commercial power supply is not readily available, the portable computer is dependent on the power provided by the battery which is incorporated in the computer apparatus.
When a small battery is used to reduce weight and cost, a relatively low voltage and small magnitude of current is available for use. A low current supply results in an increase in time required for job execution by the disk drive, such as positioning the magnetic head arm assembly to access selected data tracks on the surface of a magnetic disk.
For head positioning operation in a disk drive, current is supplied to a head actuator comprising a winding or coil which is located within a magnetic field provided by permanent magnets or pole pieces. The head actuator is coupled to a head arm which supports a magnetic transducer for coaction with the surface of a magnetic disk for recording and reading data. The direction of current in the coil determines the direction of radial travel of the head arm and transducer relative to the circular data tracks on the disk surface. The speed of head positioning to access the selected data tracks is dependent on the power supplied to the head actuator. To achieve high performance operation, particularly when a hard disk drive is used with the portable computer, a large amount of power greater than the power provided by the conventional battery supply is required.